viewgroup简单说就是可以装view的view.今天遇到一个问题,就是需要一个可以自动根据一行中view的宽度自动换行的布局,网上找了下,没有相关的例子,但是找到了思路:自定义一个viewgroup,然后在onlayout文件里面自动检测view的右边缘的横坐标值,和你的view的parent view的况度判断是否换行显示view就可以了。因为代码比较简单,就不多说了:
public class MyViewGroup extends ViewGroup { private final static String TAG = "MyViewGroup"; private final static int VIEW_MARGIN=2; public MyViewGroup(Context context) { super(context); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { Log.d(TAG, "widthMeasureSpec = "+widthMeasureSpec+" heightMeasureSpec"+heightMeasureSpec); for (int index = 0; index < getChildCount(); index++) { final View child = getChildAt(index); // measure child.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED); } super.onMeasure(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) { Log.d(TAG, "changed = "+arg0+" left = "+arg1+" top = "+arg2+" right = "+arg3+" botom = "+arg4); final int count = getChildCount(); int row=0;// which row lay you view relative to parent int lengthX=arg1; // right position of child relative to parent int lengthY=arg2; // bottom position of child relative to parent for(int i=0;i<count;i++){ final View child = this.getChildAt(i); int width = child.getMeasuredWidth(); int height = child.getMeasuredHeight(); lengthX+=width+VIEW_MARGIN; lengthY=row*(height+VIEW_MARGIN)+VIEW_MARGIN+height+arg2; //if it can't drawing on a same line , skip to next line if(lengthX>arg3){ lengthX=width+VIEW_MARGIN+arg1; row++; lengthY=row*(height+VIEW_MARGIN)+VIEW_MARGIN+height+arg2; } child.layout(lengthX-width, lengthY-height, lengthX, lengthY); } } }
这里有个地方要注意,那就要明白ViewGroup的绘图流程:ViewGroup绘制包括两个步骤:1.measure 2.layout
在两个步骤中分别调用回调函数:1.onMeasure() 2.onLayout()
1.onMeasure() 在这个函数中,ViewGroup会接受childView的请求的大小,然后通过childView的 measure(newWidthMeasureSpec, heightMeasureSpec)函数存储到childView中,以便childView的getMeasuredWidth() andgetMeasuredHeight() 的值可以被后续工作得到。
2.onLayout() 在这个函数中,ViewGroup会拿到childView的getMeasuredWidth() andgetMeasuredHeight(),用来布局所有的childView。
3.View.MeasureSpec 与 LayoutParams 这两个类,是ViewGroup与childView协商大小用的。其中,View.MeasureSpec是ViewGroup用来部署 childView用的, LayoutParams是childView告诉ViewGroup 我需要多大的地方。
4.在View 的onMeasure的最后要调用setMeasuredDimension()这个方法存储View的大小,这个方法决定了当前View的大小。
http://www.cnblogs.com/slider/archive/2011/11/24/2262161.html
还可以试试这个:
import android.content.Context; import android.util.AttributeSet; import android.view.View; import android.view.ViewGroup; /** * * @author RAW */ public class FlowLayout extends ViewGroup { private final static int PAD_H = 2, PAD_V = 2; // Space between child views. private int mHeight; public FlowLayout(Context context) { super(context); } public FlowLayout(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { assert (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.UNSPECIFIED); final int width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight(); int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom(); final int count = getChildCount(); int xpos = getPaddingLeft(); int ypos = getPaddingTop(); int childHeightMeasureSpec; if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST) childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.AT_MOST); else childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); mHeight = 0; for(int i = 0; i < count; i++) { final View child = getChildAt(i); if(child.getVisibility() != GONE) { child.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.AT_MOST), childHeightMeasureSpec); final int childw = child.getMeasuredWidth(); mHeight = Math.max(mHeight, child.getMeasuredHeight() + PAD_V); if(xpos + childw > width) { xpos = getPaddingLeft(); ypos += mHeight; } xpos += childw + PAD_H; } } if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED) { height = ypos + mHeight; } else if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST) { if(ypos + mHeight < height) { height = ypos + mHeight; } } height += 5; // Fudge to avoid clipping bottom of last row. setMeasuredDimension(width, height); } // end onMeasure() @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { final int width = r - l; int xpos = getPaddingLeft(); int ypos = getPaddingTop(); for(int i = 0; i < getChildCount(); i++) { final View child = getChildAt(i); if(child.getVisibility() != GONE) { final int childw = child.getMeasuredWidth(); final int childh = child.getMeasuredHeight(); if(xpos + childw > width) { xpos = getPaddingLeft(); ypos += mHeight; } child.layout(xpos, ypos, xpos + childw, ypos + childh); xpos += childw + PAD_H; } } } // end onLayout() }
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